Piovesan, R. (2014). Characterising the unique polychrome sinopia under the Lod Mosaic, Israel: pigments and painting technique. Journal of Archaeological Science. 6, 68–74.
A PDF of the full article is available on the internet.
Abstract; A sinopia, usually a monochrome preparatory drawing made on a mortar substrate, was used in the Graeco-Roman world either as a base for frescoes or to facilitate the application of coloured mosaic tesserae on walls or floors. In 2009, during the detachment of the Lod Mosaic (Israel), an unexpected and, for the Classical Roman era, a unique, polychrome sinopia was revealed under one of the floor panels. The palette of colours includes red and yellow ochre, green earth, carbon black and the valuable red pigment cinnabar, all applied with the fresco technique, as attested by microstratigraphy.
Sinopia, painted guidelines, Lod mosaic, Israel, 300 AD. This shows the setting bed where the guidelines have been painted onto the wet mortar into which the tesserae are pressed. copyright Lawrence Payne/Roman Mosaic Workshops 2014. You can use this image but please attach the copyright details, thanks.